Method of making improved fiber glass mat, laminates made with the mat, and method of making laminates

ABSTRACT

A method of making a fiber glass mat especially useful for bonding to wood contains glass fibers and a “B” staged resin is disclosed. A substantial portion of the resin binder can be a furfuryl alcohol formaldehyde, phenol formaldehyde, melamine formaldehyde, or any other resin that can be “B” staged. Also, a method of making wood and wood product laminates using this new mat without any other adhesives, and the resultant laminates are disclosed.

[0001] This application is a division and continuation in part of U.S.application Ser. No. 08/728,655, filed Oct. 10, 1996.

[0002] The present invention involves a method of making mats havingparticular use in bonding to wood and in making improved wood productsand the method of making such mats. The mats produced according to thisinvention are useful as reinforcement and dimensional stabilizers formaking a large number of novel laminate products such as wood laminatesof all types, hard faced wood products such as plywood and hardboard formaking concrete forms and many other similar uses. The mats are alsouseful as stabilizing and reinforcing substrates for various otherproducts. The invention also includes the method of making the laminatesand the resulting laminates.

BACKGROUND

[0003] It is known to make reinforcing mats from glass fibers and to usethese mats as substrates in the manufacture of a large number of roofingproducts. Any known method of making nonwoven mats can be used, such asthe conventional wet laid processes described in U.S. Pat. Nos.4,112,174, 4,681,802 and 4,810,576, the disclosures of which areincorporated herein by reference. In these processes a slurry of glassfiber is made by adding glass fiber to a typical white water in a pulperto disperse the fiber in the white water forming a slurry having a fiberconcentration of about 0.2-1.0 weight %, metering the slurry into a flowof white water to dilute the fiber concentration to 0.1 or below, anddepositing this mixture on to a moving screen forming wire to dewaterand form a wet nonwoven fibrous mat.

[0004] This wet nonwoven mat of glass fiber is then transferred to asecond moving screen and run through a binder application saturatingstation where an aqueous binder mixture, such as an aqueous ureaformaldehyde (UF) resin based binder mixture, is applied to the mat inany one of several known ways. The binder saturated mat is then run overa suction section while still on the moving screen to remove excessbinder. The wet mat is then transferred to a wire mesh moving belt andrun through an oven to dry the wet mat and to cure (polymerize) the UFbased resin binder which bonds the fibers together in the mat.Preferably, the aqueous binder solution is applied using a curtaincoater or a dip and squeeze applicator, but other methods of applicationsuch as spraying will also work.

[0005] In the drying and curing oven the mat is subjected totemperatures up to 450 or 500 degrees F. for periods usually notexceeding 1-2 minutes and as little as a few seconds. Alternativeforming methods include the use of well known processes of cylinderforming, continuous strand mat forming which lays continuous strands ofglass fibers in overlapping swirls, and “dry laying” using carding orrandom fiber distribution.

[0006] UF resins, usually modified with one or more of acrylic, styrenebutadiene, or vinyl acetate resins, are most commonly used as a binderfor fiber glass mats because of their suitability for the applicationsand their relatively low cost. Melamine formaldehyde resins aresometimes used for higher temperature and/or chemical resistantapplications. To improve the toughness of the mats, a combination ofhigher mat tear strength and mat flexibility, which is needed to permithigher processing speeds on roofing product manufacturing lines and formaximum roofing product performance on the roofs and in otherapplications, it is common to modify or plasticize the UF resins asdescribed above.

[0007] Mats made in the above described manner perform well in manyapplications, but do not provide the bonding strength desired forbonding to wood products.

SUMMARY OF THE INVENTION

[0008] In the conventional processes of making a nonwoven fiber mat bythe processes described above, a slurry of fiber, preferably glassfiber, is metered into a stream of whitewater, preferably cationic tononionic, and formed into a wet nonwoven mat on a moving, permeablesurface and the mat is thereafter bounded with an aqueous ureaformaldehyde (UF) binder, preferably an aqueous UF binder in water andmodified by mixing in polyvinyl acetate and/or acrylic tripolymer, driedand cured. The present invention uses this general process to make mats,but includes the improvement of using a different binder resin, anaqueous furfuryl alcohol formaldehyde, phenol formaldehyde, melamineformaldehyde, mixtures of these resins in aqueous solution and othersimilar resins, to produce mats in which the resin binder is dried and“B” staged, i. e. only partially cured. In a “B” staged condition theresin binder provides adequate strength to handle and further processthe mat, but retains the ability to bond to wood and to “flow” (plasticdeformation) under heat and pressure prior to finally curing, much likea thermoplastic resin, permitting densification of the fiber glass matwithout damaging the fibers before becoming fully cured, i. e.thermoset.

[0009] The mats of the present invention comprise glass fibers bondedtogether with a resin binder wherein the resin binder is only partiallycured to a “B” stage condition. The mats of the present invention havelower physical properties initially like tensile strength, hot wetstrength and tear strength than conventionally cured mats, but the matsof the present invention surprisingly produce substantially higherbonding strength with wood.

[0010] These mats are then used in the manufacture of wood productswherein one or more layers of the inventive mat are bonded to one ormore layers of wood or a wood product like particle board, chip board,oriented strand board, plywood, hardboard, etc., and the resultinglaminate are then subjected to high pressure and sufficient heat tofinish curing the “B” staged resin in the mat, and any additional resinthat might be used to bond the mat to the wood. Wood products andlaminates made using the mats of the present invention are a part of thepresent invention and have surprisingly good rigidity and strengths, andwhen the inventive mats are bonded to the surface of wood or a woodproduct, the resultant wood product has a surprisingly tough surface.The “B” staged resin in the mat must be compatible with thethermosetting laminating glues used in the wood composite industry,including urea formaldehyde, phenol formaldehyde, melamine formaldehydeand hot melts.

[0011] The mats of the present invention can also contain pigments,dyes, flame retardants, and other additives so long as they do notsignificantly reduce the ability of the mat to bond to a wood surface.The pigments or other additives can be included in the fiber slurry, thebinder slurry or can be sprayed or otherwise coated onto the mat laterusing known techniques.

DETAILED DESCRIPTION OF THE INVENTION

[0012] Mats of the present invention contain about 25-75 weight percentfibers and about 15-75 percent binder. The majority of the fibers areglass fibers. The glass fibers which can be used to make mats can havevarious fiber diameters and lengths dependent on the strength and otherproperties desired in the mat as is well known. It is preferred that themajority of the glass fibers have diameters in the range of less than 1up to 23 microns or higher, with the major portion of the fiber beingpreferably in the range of about 6 to 19 microns and most preferably inthe range of about 8 to 16 microns. Up to 50 percent of the glass fibersin the mat, on a weight basis can be microfiber, i. e. fiber havingaverage diameters below 1 micron but, including fiber having averagediameters up to 3 microns. The glass fibers can be E glass, C glass, Tglass, S glass or any known glass fiber of good strength and durabilityin the presence of moisture. Normally the glass fibers used all haveabout the same target length, such as 0.25, 0.5, 0.75, 1 or 1.25 inch,but fibers of different lengths and different average diameters can alsobe used to get different characteristics in a known manner. Microfibers,by their nature, will usually have random lengths under 0.25 inch.Fibers up to about 3 inches in length can be used in a wet process formaking fiber glass mats and even longer fibers can be used in some dryprocesses. Generally the longer the fiber, the higher the tensile andtear strengths of the mat, but the poorer the fiber dispersion.

[0013] While the majority of the fibers used in the present inventionare glass fibers, a minor portion of non-glass fibers can also be used,such as cellulosic fibers including wood pulp of all kinds, cottonlinters, cellulose derivatives such as cellulose triacetate, rayon, etc.Man made organic fibers such as Nylons, polyester, polyethylene,polypropylene, etc. can also be used instead of cellulose fibers in anyvarious blends with one or more cellulosic fibers. As will be seenlater, it is particularly advantageous to have a higher concentration ofcellulosic fibers on one or both surface portions of the mat, extendinginto the mat thickness a small distance, with a higher concentration ofglass fibers in the center portion of the mat to enhance bonding of themat to wood.

[0014] The binders used to bond the fibers together are resins that canbe put into aqueous solution or emulsion latex, that can be “B” staged,and that bond good to wood. Typical resin based binders meeting thisdescription are furfuryl formaldehyde, phenol formaldehyde resole andmelamine formaldehyde and other similar resins. Of these, furfurylformaldehyde resin is much preferred because of its bonding power towood, its ease to “B” stage cure, its reduced levels of volatile organiccompound (VOC) emissions, its zero phenol content and its stability instorage. Furan resins of the type useful in this invention are describedin U.S. Pat. No. 5,545,825, the disclosure of which is herebyincorporated herein by reference.

[0015] A particularly useful furfuryl alcohol formaldehyde resin for usein this invention is a FAREZ® resin, such as XP4, available from GreatLakes Chemical Corporation of West Lafayette, Indiana. This resin is afurfuryl alcohol based, highly reactive, water compatible resincontaining low levels of volatile components. It has a specific gravityof 1.24 grams/cc, contains 17-21 percent water, has a viscosity of800-1200 cps., a maximum furfuryl alcohol content of about 1 percent, amaximum free formaldehyde content of about 4 percent and a pH of 4-5.This resin contains only about 2 percent non furfuryl alcohol componentswhich are typically about 0.05 percent water, about 0.3-0.7 percentfurfural, and about 0.5 percent 2-methyl furfuryl alcohol. this resin isfully compatible with numerous phenolic, urea and melamine resin basedbinders.

[0016] A particularly useful phenol formaldehyde resin for use in thepresent invention is GP 144D64, a plasticized phenolic resin availablefrom Georgia Pacific. Another resin useful is a methylated, lowformaldehyde melamine formaldehyde resin like Astromel® CR-1 availablefrom Astro Industries, a division of Borden, Inc.

[0017] When these resins are used conventionally as a binder it isnormal to add a strong acid catalyst in the aqueous binder solution andto cure at temperatures above about 350 degrees F. to fully and quicklycure the binder, providing hot wet strengths(soaked for 10 minutes in180 degree F. water) of 90-100 percent. To “B” stage these resins in thepresent invention, very little or even no cure catalyst need be used,but in this case “B” stage cure temperatures of about 375 to 400 degreesis required. Preferably, up to about 10 weight percent, based on theweight of resin in the mat, most preferably about 5 to 10 weightpercent, of a cure catalyst like ammonium nitrate is used to speed “B”staging at a relatively low temperature. The mat is cured attemperatures between about 300 and about 350 degrees F., such as 340degrees F., for very short times, only 5-120 seconds, preferably 20-120seconds. If the cure temperature is much less than 330 degrees F., theresultant mat will not have adequate strength for handling andprocessing in the intended uses to avoid damage. If the cure temperatureis much above 360 degrees F. the resin could cure too much and the matwill not bond as well to wood later. Other catalysts can be used, suchas organic aromatic acids like para-toluene sulfonic acid and organicacids like maleic acid.

[0018] Processes for making nonwoven fiber glass mats are well known andsome of them are described in U.S. Pat. Nos. 4,112,174, 4,681,802 and4,810,576, which references are hereby incorporated into this disclosureby reference, but any known method of making nonwoven mats can be used.The preferred technique for the making of mats of the present inventionis forming a dilute aqueous slurry of fibers and depositing the slurryonto an inclined moving screen forming wire to dewater the slurry andform a wet nonwoven fibrous mat, on machines like a Hydroformer™manufactured by Voith—Sulzer of Appleton, Wis., or a Deltaformer™manufactured by Valmet/Sandy Hill of Glenns Falls, N.Y.

[0019] Next, the wet, unbonded mat is transferred to a second movingscreen running through a binder application saturating station where thefurfuryl alcohol formaldehyde resin based binder in aqueous solution isapplied to the mat. The excess binder is removed, and the wet mat istransferred to a moving oven belt where the unbonded, wet mat is driedand cured to only a “B” stage, bonding the fibers together in the mat.The partially cured mat is then usually wound into rolls and packaged.Mats made with the furfuryl alcohol formaldehyde resin binder can bestored without being protected from a humid atmosphere, but mats madewith phenolic resin or melamine formaldehyde resin binder should bestretch wrapped or shrunk wrapped or put into a plastic bag since thesebinders are hydroscopic and will take on moisture from a humidatmosphere.

[0020] The aqueous binder solution is preferably applied using a curtaincoater or a dip and squeeze applicator. In the drying and curing oventhe mat is heated to temperatures of up to about 350 degrees F., butthis can vary from about 210 degrees F. to as high as any temperaturethat will not take the mat beyond “B” stage cure. The treatment time atthese temperatures can be for periods usually not exceeding 1 or 2minutes and frequently less than 40 seconds. The lower the temperatureselected for the cure, the longer time required to reach “B” stage cure,but normally a temperature is selected that will reach “B” stage cure inno more than a few seconds, which is required on a commercial continuousglass mat manufacturing line.

EXAMPLE 1

[0021] A fiber slurry was prepared in a well known manner by adding 0.5inch long wet E type glass chopped fiber having fiber diametersaveraging about 10 microns to a known cationic white water containingNatrosol™ thickening agent available from Hercules, Inc. and a cationicsurfactant C-61, an ethoxylated tallow amine available from CytecIndustries, Inc. of Morristown, N.J., as a dispersing agent to form afiber concentration of about 0.8 weight percent. After allowing theslurry to agitate for about 20 minutes to thoroughly disperse thefibers, the slurry was metered into a moving stream of the samewhitewater to dilute the fiber concentration to a concentrationaveraging about 0.05 to 0.06 weight percent before pumping the dilutedslurry to a headbox of a Voith Hydroformer™ where a wet nonwoven mat wascontinuously formed.

[0022] The wet mat was removed from the forming wire and transferred toa Sandy Hill Curtain Coater where an aqueous UF binder (the GeorgiaPacific UF described above), modified with (mixed with) about 24 weightpercent, based on the dry weight of the UF resin, of a blend of 91.7weight percent polyvinyl acetate homopolymer and 8.3 weight percent ofan acrylic tripolymer, was applied in an amount to provide a binderlevel in the cured mat of about 19-20 weight percent. The wet mat wasthen transferred to an oven belt and carried through an oven to dry themat and to fully cure the modified UF resin to a temperature of about450 degrees F. The basis weight of the mat produced was 8.7 grams persquare foot. The mat, containing 80-81 weight percent 10 micron E glassfiber and 19.5-21 percent modified urea formaldehyde binder, had thefollowing strength properties: Hot Wet Tensile 90+ percent (10 minutesin 180 degree F. water) Thickness 32-33 mils Loss On Ignition 19.5-21weight percent Machine Direction Tensile 109 lbs./3 inches Cross MachineDirection Tensile  80 lbs./3 inches Machine Direction Tear Strength 500grams Cross Machine Dir. Tear Strength 600 grams

[0023] A 6 inch by 6 inch layer of this mat was placed between two 6inch by 6 inch layers of softwood veneer, each having a thickness ofabout 0.10 inch. This stack was put into a hot press subjected to apressure of about 77 psi and a temperature of about 350 degrees F. forabout 5 minutes. After cooling the pressure was released and the stackwas taken from the press. There was no bond between the wood layers andthe mat layer.

EXAMPLE 2

[0024] Another mat was made in exactly the same way as in Example 1,except that the average fiber diameter was 10 micron and the binderapplied to the wet nonwoven mat was an aqueous solution of FAREZ® X4Pfurfuryl alcohol formaldehyde (FAF) resin binder and the wet mat wasdried and then heated to about 300-350 degrees F. for 1-2 minutes to “B”stage the resin binder. This finished mat contained 62.3 weight percent0.75 inch long, 13 micron E glass fiber and 37.7 percent “B” staged FAFresin and had a basis weight of 1.7 lbs./100 square feet. the followingphysical properties: Volatiles in the mat 6 weight percent (based onresin weight) Thickness 27 mils Hot wet tensile 31 percent Loss OnIgnition 37.7 weight percent Machine Direction Tensile 31 lbs./3 inchwide sample Cross Machine Tensile 29 lbs./3 inch wide sample

[0025] The mat made in Examples 1 and 2 above were used to make alaminated wood sandwich in the same manner as described in Example 1except that the sandwich was subjected to 375 degrees F. for about 90seconds at the same pressure. The same test was repeated usingone-eighth inch hardboard instead of the softwood veneer. In both cases,the mat of Example 2 bonded the wood veneer and hardboard togethertightly such that they could not be pulled apart by hand.

[0026] A layer of mat made according to this example was then placed ontop of one layer of the softwood veneer and a Teflon® separator sheetwas placed on top of the mat before putting the sandwich into the press.This sandwich was pressed under the same conditions as above andremoved. When the separator sheet was removed (it didn't bond to themat) the mat was bonded tightly to the wood veneer and provided a toughsurface that would act to dimensionally stabilize the layer of wood andprotect the wood from physical abuse.

EXAMPLE 3

[0027] A mat was made as in Example 2, except that the basis weight wasincreased to 5.1 lbs./100 sq. ft. The mat properties were as follows:

[0028] Volatiles—5.3 wt. percent of resin in mat

[0029] Hot wet strength—23 percent

[0030] Thickness—29 mils

[0031] Machine Direction (MD) Tensile Strength—48 lbs./3 inches

[0032] Cross Machine (CMD) Tensile Strength—46 lbs./3 inches

[0033] Mat made in this example was tested in the same manner as the matin Example 2 and the results were even better.

EXAMPLE 4

[0034] Mat was made exactly the same as in Example 1 except that theresin used was Georgia Pacific's 144D64 phenol formaldehyde (PF) and themat was dried and heated to 320 degrees F. for 5 minutes to “B” stagethe PF resin binder. The finished mat contained 52.5 percent glass fiberand 47.5 percent “B” staged PF resin, was very hydroscopic and had thefollowing properties:

[0035] Basis weight—3 lbs./100 sq. ft.

[0036] Volatiles—4.3 percent of the resin

[0037] Thickness—35 mils

[0038] Hot wet tensile—0 percent

[0039] MD tensile—70 lbs./3 inches

[0040] CMD tensile—60 lbs./3 inches

[0041] This mat was tested in the same manner as described in Example 2and produced similar results as the “B” staged FAF resin bound mat.

[0042] This mat was also laminated to each face of a one eighth inchthick hardboard and to each side of a one half inch thick orientedstrand board using the laminating procedure described in Example 2.Samples were cut from these two laminates and from the unfaced hardboardand unfaced oriented strand board. All of these samples were then testedfor modulus of rupture, flexural strength, with the well known threepoint loading procedure. The results were as follows: TABLE SampleModulus of Rupture (psi) % Change Hardboard 80 0 Mat/hardboard/matlaminate 114 +42.5 Oriented Strand Board (OSB) 125 0 Mat/OSB/Mat 173+38.4

[0043] The mat layers did not delaminate from either the hardboard orthe OSB preceding or during failure of the laminate, but instead brokewith the hardboard and the OSB. This higher flex strength of thelaminates means that laminate beams made with the mats of the presentinvention and in accordance with the present invention can span greaterlengths, support greater loads or both compared with laminates of thewood products alone.

EXAMPLE 5

[0044] Mat was made exactly the same as in Example 1 except that theresin used was Borden's Astromel® CR-1 melamine formaldehyde (MF) resindescribed earlier in the specification and the mat was dried and heatedto 320 degrees F. for 1-2 minutes to “B” stage the MF resin binder. Thefinished mat had the following properties:

[0045] Basis weight—2.3 lbs./100 sq. ft.

[0046] Thickness—26 mils

[0047] Hot wet strength—less than 10 percent

[0048] MD tensile—35 lbs./3 in.

[0049] CMD tensile—27 lbs./3 in.

[0050] This mat was tested in the same manner as described in Example 2and showed similar results.

[0051] While the preferred embodiments of the invention have beendisclosed in detail, other embodiments within the described inventionand having other functional additives known or obvious to those skilledin the art are considered as part of the present invention and areintended to be included in the invention claimed below.

I claim:
 1. A method of making a fiber glass mat for bonding to wood orto a wood product wherein an aqueous mixture comprising a binder isapplied to a wet, nonwoven mat of unbonded, crossing glass fibersfollowed by drying said mat and curing said resin to form a bonded glassfiber mat, the improvement comprising drying and curing the mat onlypartially to “B” stage the resin binder.
 2. The method of claim 1wherein the major portion of the mat is glass fibers.
 3. The method ofclaim 1 wherein cellulosic fibers or fibers of a cellulose derivativeare mixed with the glass fibers to make said mat.
 4. The method of claim1 wherein a substantial portion of the resin binder is selected from agroup consisting of furfuryl alcohol formaldehyde based resin, phenolformaldehyde resin and melamine formaldehyde resin.
 5. The method asdescribed in claim 2 wherein a substantial portion of the resin binderis selected from a group consisting of furfuryl alcohol formaldehydebased resin, phenol formaldehyde resin and melamine formaldehyde resin.6. The method as described in claim 3 wherein a substantial portion ofthe resin binder is selected from a group consisting of furfuryl alcoholformaldehyde based resin, phenol formaldehyde resin and melamineformaldehyde resin.
 7. The method as described in claim 4 wherein asubstantial portion of the resin binder is a furfuryl alcoholformaldehyde based resin.
 8. The method as described in claim 5 whereina substantial portion of the resin binder is a furfuryl alcoholformaldehyde based resin.
 9. The method as described in claim 6 whereina substantial portion of the resin binder is a furfuryl alcoholformaldehyde based resin.
 10. The method as described in claim 1 whereina substantial portion of the resin binder is a furfuryl alcoholformaldehyde based resin.
 11. A method of making a wood laminate or woodproduct laminate by pressing a wood or wood product against a fiberglass nonwoven mat under while being heated to complete the cure of thebinder in the mat, said mat comprising glass fibers bonded together withabout 15-75 weight percent of a resin binder wherein the resin binder isderived from an aqueous resin selected from the group consisting offurfuryl alcohol formaldehyde based resin, phenol formaldehyde resin andmelamine formaldehyde resin and is only partially cured to a “B” stagecondition and wherein said mat also contains cellulosic fibers or fibersof a cellulose derivative.
 12. The method as described in claim 11wherein the major portion of the mat is glass fibers and up to 75 weightpercent of the mat is fibers.
 13. The method as described in claim 12wherein the mat also contains a cure catalyst in the resin binder. 14.The method as described in claim 11 wherein said glass fibers are lessthan 3 inches long and are in the form of a nonwoven mat.
 15. The methodas described in claim 13 wherein said glass fibers are less than 3inches long and are in the form of a nonwoven mat.
 16. A laminate ofwood or a wood product bonded to a glass fiber nonwoven mat comprisingglass fibers bonded together with about 15-75 weight percent of a resinbinder wherein the resin binder is derived from an aqueous resinselected from the group consisting of furfuryl alcohol formaldehydebased resin, phenol formaldehyde resin and melamine formaldehyde resinand is only partially cured to a “B” stage condition and wherein saidmat also contains cellulosic fibers or fibers of a cellulose derivative.17. The method as described in claim 16 wherein the major portion of themat is glass fibers and up to 75 weight percent of the mat is fibers.18. The method as described in claim 17 wherein the mat also contains acure catalyst in the resin binder.
 19. The method as described in claim16 wherein said glass fibers are less than 3 inches long and are in theform of a nonwoven mat.
 20. The method as described in claim 18 whereinsaid glass fibers are less than 3 inches long and are in the form of anonwoven mat.